The present embodiments relate to a spindle motor.
A spindle motor is installed inside an optical disk drive (ODD), and performs the function of rotating a disk to enable an optical pickup to read data recorded on the disk.
FIG. 1 is a plan view showing a rotation shaft supported on a bearing in a spindle motor according to the related art.
Referring to FIG. 1, a rotation shaft 15 is installed to be supported and capable of rotating in a bearing 11 press-fitted and fixed in a bearing housing (not shown).
The rotation shaft 15 is coupled to a rotor (not shown), and the rotor is rotated (together with the rotation shaft 15) through interaction between a stator (not shown) and the rotor. Here, the rotation shaft 15 simultaneously rotates and orbits along the inner periphery of the bearing 11, by means of a clearance existing between the outer periphery of the rotation shaft 15 and the inner periphery of the bearing 11.
That is, the rotation shaft 15 rotates about a central axis of the rotation shaft 15, and simultaneously orbits about a center of the bearing 11.
When the rotation shaft 15 orbits about the center of the bearing 11, rotational eccentricity increases in a radial direction to the rotation shaft 15. Thus, in a related art spindle motor, the surface vibration in an axial direction of a disk mounted on the rotor that is coupled to the rotation shaft 15, or the upward and downward surface vibration, becomes severe and reduces product reliability.
In particular, when the disk is rotated at low speeds, the surface vibration in the axial direction of the disk increases, so that when a predetermined design is printed on the surface of the disk, lines to be represented overlap or are not accurately represented.